Self-reported symptom severity, general health, and impairment in post-acute phases of COVID-19: retrospective cohort study of Swedish public employees

This study aimed to examine current symptom severity and general health in a sample of primarily non-hospitalized persons with polymerase chain reaction (PCR) confirmed COVID-19 in comparison to PCR negative controls. During the first quarter of 2021, we conducted an online survey among public employees in West Sweden, with a valid COVID-19 test result. The survey assessed past-month severity of 28 symptoms and signs, self-rated health, the WHO Disability Assessment Schedule (WHODAS) 2.0 and illness severity at the time of test. We linked participants’ responses to their SARS-CoV-2 PCR tests results. We compared COVID-19 positive and negative participants using univariable and multivariable regression analyses. Out of 56,221 invited, 14,222 (25.3%) responded, with a response rate of 50% among SARS-CoV-2 positive individuals. Analysis included 10,194 participants (86.4% women, mean age 45 years) who tested positive 4–12 weeks (N = 1425; subacute) and > 12 weeks (N = 1584; postcovid) prior to the survey, and 7185 PCR negative participants who did not believe that they had had COVID-19. Symptoms were highly prevalent in all groups, with worst symptoms in subacute phase participants, followed by postcovid phase and PCR negative participants. The most specific symptom for COVID-19 was loss of smell or taste. Both WHODAS 2.0 score and self-rated health were worst in subacute participants, and modestly worse in postcovid participants than in negative controls. Female gender, older age and acute illness severity had larger effects on self-rated health and WHODAS 2.0 score in PCR positive participants than in PCR negative. Studies with longer follow-up are needed to determine the long-term improvement after COVID-19.


Contents:
p. 2  Table S1. Prevalence of symptoms according to severity among subacute phase, postcovid phase and PCR negative participants.
p. 5 Table S2. Relative symptom severity among subacute and postcovid phase COVID-19 positive participants, compared to PCR negative participants p. 6 Table S3. Effect of time on symptom severity among subacute phase participants p. 7 Table S4. Effect of time on symptom severity among postcovid phase participants p. 8 Table S5. Mean scores and relative scores of WHODAS 2.0 in subgroups with significant interaction effects for subacute or postcovid phase participants p. 9 Table S6. Self-rated health in subgroups with significant interaction effects for subacute or postcovid phase participants p. 11 Table S7. P-values of the association between interaction terms between COVID-19 status and other variables. and self-rated health and WHODAS 2.0 score p. 12 Table S8. Association between time since positive test, WHODAS 2.0 score and self-rated health in subacute and postcovid phase participants p. 13 STROBE statement Table S1. Prevalence of symptoms according to severity among subacute phase, postcovid phase and PCR negative participants.

Introduction
Background/rationale 2 Explain the scientific background and rationale for the investigation being reported 3 "these symptoms are among the most frequently occurring symptoms in the general population. Therefore, in order to establish valid diagnostic criteria, and to estimate contribution to disease and impairment, it is important to examine how the health of persons in the post-acute phase of COVID-19 differ from comparable uninfected individuals" Objectives 3 State specific objectives, including any prespecified hypotheses 4 "to examine the long-term excess in symptom severity and functional impairment following COVID-19, we designed a study…"

Study design 4
Present key elements of study design early in the paper 4 "…public employees included in an extensive PCR testing program, irrespective of SARS-CoV-2 positivity, were invited to complete an online survey…"

12
(a) Describe all statistical methods, including those used to control for confounding 9-10 (b) Describe any methods used to examine subgroups and interactions 9 "Next, we explored if determinants of WHODAS 2.0 score and self-rated health differed depending on COVID-19 status. We conducted models including each variable of interest, COVID-19 status and their interaction term." (c) Explain how missing data were addressed 5 "We could only view and export data from participants who had completed and submitted the questionnaire in its whole."… "BMI could not be calculated for five participants due to obviously unlikely reported values." (d) Cohort study-If applicable, explain how loss to follow-up was addressed Case-control study-If applicable, explain how matching of cases and controls was addressed Cross-sectional study-If applicable, describe analytical methods taking account of sampling strategy 9 "We adjusted [our analyses]} for exposure to COVID-19 patients at work and occupation, since these two variables could act as confounders." (e) Describe any sensitivity analyses -None performed

Results
Participants 13* (a) Report numbers of individuals at each stage of study-eg numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed 11, Figure 1 (b) Give reasons for non-participation at each stage Figure 1 (c) Consider use of a flow diagram Figure 1 Descriptive data 14* (a) Give characteristics of study participants (eg demographic, clinical, social) and information on exposures and potential confounders 11-12,